Control of Rosellinia necatrix in Soil and in Apple Orchard by Solarization and Trichoderma harzianum

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Abstract
Various types of natural or culturally produced inocula of Rosellinia necatrix (anamorph: Dematophora necatrix) are highly sensitive to heat; 50-100% mortality was recorded after 4 hr at 38.degree.C. Inoculum of the pathogen in inoculated wheat seeds became less heat-sensitive after aging. In one of two soils, combining sublethal heating in the laboratory with application of Trichoderma harzianum further improved pathogen control over that achieved by either treatment alone. Solarization by polyethylene tarping of the soil resulted in effective control of the pathogen and disease (as assessed by various methods). Partial or complete pathogen control was obtained in tarped-shaded (unheated) plots. Growth of the pathogen was reduced in a previously solarized soil, as assessed by leaf colonization and mycelial growth methods, thus indicating soil suppressiveness. Soil solarization of an existing orchard with infected apple trees reduced disease considerably over at least 25 mo. T. harzianum was not effective in disease control under the tested field conditions.